Method and mechanism of the suspension resonance optimization for the hard disk driver

ABSTRACT

A system and method are disclosed for using a test slider to test the resonance performance of a head gimbal assembly. The test slider has a two-stripe air-bearing surface to allow the test slider to glide above a surface and a block with a mass equal to the combined mass of the electrical slider and the micro-actuator. The leading edge of the slider is tapered and has a main air groove to facilitate gliding. A back step on the side of the test slider opposite the air bearing surface maintains a parallel gap between the slider and the suspension tongue of the head gimbal assembly.

BACKGROUND INFORMATION

The present invention is directed to attaching a slider to a headsuspension. More specifically, the present invention pertains toreducing the amount of adhesive needed to couple the slider to the headsuspension.

FIG. 1 illustrates a hard disk drive design typical in the art. Harddisk drives 100 are common information storage devices consistingessentially of a series of rotatable disks 104 that are accessed bymagnetic reading and writing elements. These data transferring elements,commonly known as transducers, are typically carried by and embedded ina slider body 110. The slider 110 is held in a close relative positionby a head gimbal assembly (HGA), including a suspension 102 attached toan actuator arm 106, over discrete data tracks formed on a disk topermit a read or write operation to be carried out. The HGA is rotatedaround a pivot 108 by a voice coil motor 112. In order to properlyposition the transducer with respect to the disk surface, an air bearingsurface (ABS) formed on the slider body 110 experiences a fluid air nowthat provides sufficient lift force to “fly” the slider 110 (andtransducer) above the disk data tracks. The high speed rotation of amagnetic disk 104 generates a stream of air flow or wind along itssurface in a direction substantially parallel to the tangential velocityof the disk. The air flow cooperates with the ABS of the slider body 110which enables the slider to fly above the spinning disk. In effect, thesuspended slider 110 is physically separated from the disk surface 104through this self-actuating air bearing. The ABS of a slider 110 isgenerally configured on the slider surface facing the rotating disk 104(see below), and greatly influences its ability to fly over the diskunder various conditions.

FIGS. 2 a-d illustrates a prior art method for coupling a slider 110 andmicro-actuator 202 to the suspension 102 of an actuator arm 104. Asshown in FIG. 2 a, a slider 110 is coupled to a micro-actuator 202. Themicro-actuator 202 provides a finer degree of slider movement controlthan the actuator arm 104. The micro-actuator 202 has a base 204 withtwo arms 206 projecting from the base 204. A stripe of piezoelectric(PZT) material 208 is coupled to the side of each actuator arm 206. Anelectric charge applied to the PZT stripe 208 causes it to expand orcontract, moving the actuator arms 206. The slider 110 is bonded to theactuator arms 206 at the bonding points 210.

As shown in FIG. 2 b, the micro-actuator 202 is couple to the suspension102 via a suspension tongue 212. The suspension 102 is coupled to a baseplate 214. The base plate has a hole 216 that allows the base plate 214to rotate around a pivot. A series of traces 218 run the length of thesuspension 102 and suspension tongue 212 to be electrically coupled tothe slider 110 and the micro-actuator 202. The traces 218 areelectrically coupled to a control circuit via a series of bonding pads220 mounted on the base plate 214. As shown in FIG. 2 c, themicro-actuator 202 is positioned so as to maintain a gap 222 between itand the suspension tongue 212 and by extension between the slider 110and the suspension tongue 212.

The resonance performance of the suspension is a major factor in theresonance control of the HGA. The resonance performance is optimizedduring the manufacturing process in order to improve resonance control.The traditional method for testing the resonance performance of thesuspension is to use a mechanical HGA. As shown in FIG. 2 d, an actualslider 110 is fully potted to the suspension tongue 212 to create amechanical HGA. The mechanical HGA is loaded into a resonance tester.The resonance tester can use a laser Doppler to monitor or sample thefrequency response during mechanical shaking of the HGA base plate.Corrections can be made to the manufacturing process or the design basedon the results of the test. The slider in this instance is easilyrecycled after testing is completed.

This testing method becomes more difficult for an HGA that includes amicro-actuator. Mounting the micro-actuator in addition to the sliderrequires a much more accurate mounting machine or fixture, mainly tomaintain a parallel gap between the micro-actuator and the suspensiontongue. Additionally, the micro-actuator is not so easily used andrecycled as the micro-actuator is fragile and its manufacture isdifficult and expensive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a hard disk drive design typical in the art.

FIGS. 2 a-d illustrates a prior art method for coupling a slider andmicro-actuator to the suspension of an actuator arm.

FIGS. 3 a-d illustrate a test slider 302 according to embodiments of thepresent invention.

FIGS. 4 a-b illustrate in graph form a comparison of the performance ofa slider and micro-actuator and a test slider.

FIGS. 5 a-p illustrate a process for fabricating the test slideraccording to embodiments of the present invention.

FIG. 6 illustrates in a flowchart a process for fabricating a testslider according to embodiments of the present invention.

DETAILED DESCRIPTION

A system and method are disclosed for using a test slider to test theresonance performance of a head gimbal assembly. In one embodiment, thetest slider has a two-stripe air-bearing surface to allow the testslider to glide above a surface and a block with a mass equal to thecombined mass of the electrical slider and the micro-actuator. Theleading edge of the slider is tapered and has a main air groove tofacilitate gliding. A back step on the side of the test slider oppositethe air bearing surface maintains a parallel gap between the slider andthe suspension tongue of the head gimbal assembly.

In one embodiment, the mechanical head gimbal assembly (HGA) is loadedon a removable HGA mounting block. The block is loaded onto theresonance shaker of a resonance tester. The resonance tester canprecisely measure the mechanical resonance of the HGA. The resonancetester can use a laser Doppler vibrometer to monitor or sample thefrequency response during mechanical shaking of the HGA base plate. Theresonance tester provides an output plot of the magnitude and the phasevs. the frequency. Additionally, the resonance tester provides a listingof the amplitudes and frequency of the resonance peak to be processed bya fourier analyzer. This allows the suspension resonance to becontrolled during the design and manufacture process. If the resonancefrequency shift or gain is higher than the expectation, corrections canbe made to the manufacturing process or the design based on the resultsof the test. Corrections include, for example, the modification of thegeometry of the suspension structure or the optimization of themanufacture process. The test slider is easily recycled after testing iscompleted.

FIGS. 3 a-d illustrate one embodiment of a test slider 302. Themechanical block of the test slider 302 has a mass and external formequivalent to the mass of a normal slider 110 and micro-actuator 202combined. The air bearing characteristic of the test slider issubstantially equivalent to a slider and micro-actuator. As shown inFIG. 3 a, the test slider 302 has an air bearing surface (ABS) 304,which allows the slider on a current of air above a surface, such as thehard disk of a disk drive. In the embodiment shown, the ABS 304 has twostripes. The edges 306 of each stripe 304 are tapered at the leadingedge of the test slider 302, to guide the air onto the slider ABS andease the slider take off, maintaining the head flying on the disk by aconsistent force. A main air groove 308 is located between the two ABSstripes 304. A side rail surface indentation 310 is located on the outerside of each ABS stripe 304. The side rail surface indentation 310reduces the risk of a head crash or shock to the disk due to sharpcorners when the head is loaded on and unloaded off the disk. As shownin the embodiment of FIG. 3 b, the side of the test slider opposite theABS stripes 304 may have a step 312. The step 312 can be on the leadingedge of the slider 302. As shown in FIG. 3 c, the step 312 maintains thegap 222 between the test slider 302 and the suspension tongue 212. Asshown in FIG. 3 d, the test slider 302 is coupled to the suspension 102to test the resonance control of the suspension 102. In one embodiment,the test slider 302 is coupled to the suspension 102 by partiallypotting the surface of the step 312 before mounting it to the suspensiontongue 212. Epoxy or resin may be used for coupling. Epoxy may bepartially added to the leading edge of the suspension tongue 212 or onthe step surface 312 of the testing slider for more secure mounting.

FIGS. 4 a-b illustrate in graph form a comparison of the performance ofa slider and micro-actuator and a test slider. As shown in FIG. 4 a, aresonance comparison of gain in dB to frequency in kHz for the sliderwith micro-actuator 402 and the test slider 404 produces nearlyidentical results. As shown in FIG. 4 b, a w-curve comparison of gain indB to the zenith height in millionths of an inch for the slider withmicro-actuator 406 and the test slider 408 produces nearly identicalresults.

FIGS. 5 a-p illustrate one embodiment of a process for fabricating thetest slider. As shown in FIG. 5 a, a ceramic row bar 502 is applied to alapping wheel 504. The lapping wheel 504 creates a smooth air bearingsurface 304 on the row bar 502, as shown in FIG. 5 b. As shown in FIG. 5c, the leading edge of the row bar 502 is applied to the lapping wheel504. The lapping wheel 504 creates a tapered edge 306 on the air bearingsurface 304 of the row bar 502, as shown in FIG. 5 d. As shown in FIG. 5e, a grinding wheel 506 is applied to the row bar 502. The grinding 506wheel creates side rail surface indentation 310, as shown in FIG. 5 f.As shown in FIG. 5 g, a grinding wheel 506 is again applied to the rowbar 502. The grinding 506 wheel grinds a tract across the row bar, asshown in FIG. 5 b. This tract acts as the main air groove 308, as shownin FIG. 5 i. As shown in FIG. 5 j, a grinding wheel 506 is applied tothe row bar 502. The grinding 506 wheel creates a tract 508. In oneembodiment, the tract 508 is twice the width of a side rail surfaceindentation 310. A cutting wheel 510 then cuts down the center of thetract 508, splitting the tract 508 into two side rails 310, as shown inFIG. 5 k. Alternatively, the grinding wheel 506 is used to grind throughthe row bar 502 at the center of the tract 508, with the tract 508widened to accommodate the wider wheel 506. The severed piece of the rowbar 502 is the test slider 302, as shown in FIG. 51. As shown in FIG. 5m, the edge of a grinding wheel 512 is applied to the side opposite theair bearing surface 304 to produce a step 312. In an alternateembodiment shown in FIG. 5 n, the edge of a grinding wheel 512 isapplied to the side opposite the leading edge to produce a step 312. Theresult is cleaned to produce a finished test slider 302 shown in FIG. 5p.

FIG. 6 illustrates in a flowchart one embodiment of a process forfabricating a test slider 302. The row bar 502 is lapped to create asmooth air bear surface 304 (Block 610). The row bar 502 is then lappedto create a tapered surface 306 at the leading edge (Block 620). A siderail surface indentation 310 is ground out of the edge adjacent to theleading edge of the row bar 502 on the air bearing surface 304 (Block630). The main air groove 308 is then ground out of the row bar 502 onthe air bearing surface 304 parallel to the side rail surfaceindentation 310 (Block 640). A second side rail surface indentation 508double the size of the first is ground out of the row bar 502 on the airbearing surface 304 (Block 650). The row bar 502 is then sliced throughat the center of the second side rail surface indentation 508 (Block660). A step 312 is ground out of the back of the test slider 302 (Block670). The test slider 302 is then cleaned and is ready for use (Block680).

1. A method comprising the steps of: coupling a test slider to asuspension in place of a slider with micro-actuator; and measuring aresonance and W-curve of the suspension.
 2. The method of claim 1,wherein the test slider has a mass substantially equivalent to theslider with micro-actuator.
 3. The method of claim 2, wherein the testslider has an external from substantially equivalent to the slider withmicro-actuator.
 4. The method of claim 1, wherein the test slider has aweight balance substantially equivalent to the slider withmicro-actuator.
 5. The method of claim 1, wherein the test slider has anair bearing characteristic substantially equivalent to the slider withmicro-actuator.
 6. The method of claim 1, wherein the test slider has anair bearing surface to allow the test slider to glide above a disk mediasurface.
 7. The method of claim 6, wherein the test slider has a step ona side of the block opposite the air bearing surface to maintain a gapbetween the test slider and a suspension.
 8. The method of claim 7,wherein the test slider is coupled to the suspension by partiallypotting adhesive on a surface of the step.
 9. The method of claim 1,wherein the test slider is coupled to the suspension by partial potting.10. The method of claim 1, further comprising amending mechanically thesuspension when the measured resonance is out of a predetermined scope.11. A test slider, comprising a block with a mass substantiallyequivalent to a slider with micro-actuator to represent a micro-actuatorand slider during suspension resonance testing; an air bearing surfaceto allow the block to glide above a disk media surface.
 12. The testslider of claim 11, wherein the block has an external form substantiallyequivalent to the slider with micro-actuator.
 13. The test slider ofclaim 11, wherein the block has a weight balance substantiallyequivalent to the slider with micro-actuator.
 14. The test slider ofclaim 11, further comprising a main air groove along the air bearingsurface.
 15. The test slider of claim 11, wherein the leading edge ofthe air bearing surface is tapered.
 16. The test slider of claim 11,further comprising a step on a side of the block opposite the airbearing surface to maintain a gap between the block and a suspension.17. A method, comprising: lapping a ceramic row bar to create a smoothair bearing surface; and cutting the ceramic row bar into test slidersto be coupled to suspensions.
 18. The method of claim 17, furthercomprising grinding a main air groove on the air bearing surface. 19.The method of claim 17, further comprising grinding a step on a side ofthe ceramic row bar opposite the air bearing surface to maintain a gapbetween the test slider and the suspension.